1. FIELD OF THE INVENTION
This invention relates to thermoplastic polymer compositions characterized by high melt flow, which are pelletizable and can be conveniently converted into fabric and film that is drapable.
2. DESCRIPTION OF THE PRIOR ART
Several methods have been used to produce fabric or film materials. For example, fabric can be produced by knitting, tufting, wool felting, weaving, or by non-woven means. A non-woven fabric can be produced by bonding and/or interlocking fabric materials by mechanical, chemical, thermal or solvent means, or through a combination of these means in accordance with ASTM D-1117-63, Part 24, Page 315 (1965). In a narrower sense, the term "non-woven" denotes a web or mat of fibers held together with bonding materials. Non-woven fabrics were originally developed as inexpensive substitutes for woven fabrics, and have gradually entered markets for which they are uniquely suitable, such as facings or top sheets in diapers, incontinent pads, bed pads, sanitary napkins, hospital gowns, and the like.
Sources of useable fibers include cellulosics, nylon, polyesters, polyolefins, fluorocarbons, and inorganic fibers. Other polymers include polyvinyl alcohol, polyvinyl acetate, vinyl chloride polymers, styrenebutadiene copolymers, acrylic resins, polyurethanes and the like.
Film materials can be prepared by cast or blown extrusion, compression molding, or other methods known to those skilled in the art.
U.S. Pat. No. 4,368,233 to Barkis et al discloses extrusion coating compositions for woven and non-woven polyolefin substrates which employ mixtures of high density polyethylene with other polyolefins.
U.S. Patent No. 4,426,417 to Meitner et al discloses a wiper comprised of a matrix of non-woven fibers incorporating a staple fiber mixture containing synthetic and cotton fibers.
U.S. Pat. No. 4,380,570 to Schwarz discloses an apparatus and process for forming fine fibers from molten thermoplastic polymers by extruding the molten polymer through orifices in nozzles at low melt viscosity and high temperatures. The molten fibers are accelerated to near sonic velocity by gas blown in parallel flow through small orifices surrounding each nozzle.
U.S. Pat. No. 4,568,596 to Johnson discloses a non-woven, texturized fabric produced by embossing a molten film of a polymer blend of high density polyethylene and polystyrene.
U.S. Pat. Nos. 4,211,692 and 4,255,323, both to Barkis et al, disclose extrusion coating compositions for woven and non-woven polyolefin substrates which employ an ethylene-propylene-diene terpolymer rubber, a high density polyethylene, an ethylene-propylene block copolymer and an ethylene-isobutylacrylate copolymer.
U.S. Pat. No. 4,383,925 to Hilsher et al discloses non-woven fabrics of polyolefin filament used for making filters.
U.S. Pat. No. 4,291,082 discloses breathable fabrics.
U.S. Reissue Pat. Nos. 32,028 and 30,405, both to Fischer, disclose a thermoplastic blend of partially cured mono-olefin copolymer rubber and polyolefin plastic.
U.S. Pat. No. 2,631,954 to Bright discloses a film composition formed from ethenoid polymers with an average molecular weight greater than 2500, obtained by heating ethylene in the presence of one or more organic compounds containing one or more double bonds and capable of forming dimers or high polymers.
U.S. Pat. No. 2,726,230 to Carlson discloses plastic acrylic interpolymers formed by polymerizing a monomeric mixture containing an acrylic ester and an olefinically unsaturated carboxylic acid.
U.S. Pat. No. 3,192,288 to Sayko et al discloses blends of low pressure isotactic polypropylene, polyisobutylene, and small amounts of high pressure polyethylene.
U.S. Pat. No. 4,500,681 to Shulman relates to a thermoplastic elastomeric blend of a polyolefin, an isobutylene-backbone elsstomer, and a copolymer of ethylene with an unsaturated ester of a lower carboxylic acid.
U.S. Pat. No. 4,100,240 to Bassani discloses a process for extruding a low viscosity fiber containing a polysiloxane liquid polymer precursor which reacts when heated to form a cross-linked fiber reinforced polysiloxane elastomer.
U.S. Pat. No. 4,336,212 to Yoshimura discloses a composition comprising:
(a) at least one of low density polyethylene and copolymers of ethylene with vinyl ester monomers, unsaturated aliphatic monocarboxylic acids and alkyl ester derivatives,
(b) an ethylene alpha-olefin copolymer elastomer, and
(c) at least one of crystalline polypropylene, high density polyethylene, and crystalline polybutene-1.
U.S. Pat. No. 4,341,667 to Lal et al discloses blends of reclaimed rubber devulcanized by microwave energy, with crystalline or semi-crystalline polyolefins, such as polyethylene or polypropylene.
U.S. Pat. No. 4,399,249 to Bildusas discloses a block copolymer blend containing at least two end thermoplastic polymer blocks and one mid-polymer block, wherein the end block is a non-elastomeric polymer block, and the mid-block is an elastomeric polymer block.
Despite the wealth of fabric technology, there is no known synthetic fabric which is drapable and which has a high melt flow suitable for extrusion coating or spin bonding, and which is also pelletizable.
Drapability is especially important as a comfort property in situations where the film or fabric comes into contact with human skin for extended periods of time, on the order of several hours.
Pelletizability is an important characteristic because pellets can be extruded like a thermoplastic and converted to film or fabric at high production rates in an extruder adapted with the necessary equipment for final conversion to the desired shape and form.